This application claims the benefit of Korean Patent Application No. 1999-36859, filed on Sep. 1, 1999, under 35 U.S.C. xc2xa7119, the entirety of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to an apparatus and a method of grinding a liquid crystal cell.
2. Description of the Related Art
In general, a LCD device includes a lower substrate having a thin film transistor and an upper substrate having a color filter with a liquid crystal layer interposed therebetween. A simplified manufacturing process of the liquid crystal cell is as follows. A common electrode and a pixel electrode are formed on the upper substrate and on the lower substrate, respectively. Then, the two substrates are arranged to face each other, and sealed with a sealant, thereby forming a gap between the two substrates. A liquid crystal is injected into the gap between the two substrates. Upper and lower polarizers are arranged on outer surfaces of the upper and lower substrates, respectively.
Applying voltages to the common electrode and the pixel electrode, a transmitting amount of light is controlled and a character or an image is displayed due to a light shutter effect.
A manufacturing process of the liquid crystal cell is simple in comparison to manufacturing processes of the thin film transistors and color filters. The manufacturing process of a liquid crystal cell includes the steps of forming an orientation film, forming a cell gap, and cutting a cell.
The manufacturing process of the LCD device described above is explained in detail hereinafter with reference to the accompanying drawings.
FIG. 1 is a flow chart illustrating the manufacturing process of the LCD device. As shown in FIG. 1, first the lower substrate is prepared (step 1). On the lower substrate, a plurality of thin film transistors and pixel electrodes are arranged in a one-to-one relationship. To form the orientation film on the lower substrate, the surface of the lower substrate is coated with an organic film such as a polyimide, and the orientation film is rubbed in a direction (step 2). It is desirable that the orientation film is formed to keep a uniform thickness of the whole surface over the lower substrate. The rubbing is performed normally by using a cloth. Aligned on the orientation film, the liquid crystals orient themselves uniformly in the direction of the rubbing. By the rubbing treatment of the orientation film, liquid crystals can be driven normally, and uniform display characteristics can be obtained. Then, sealant is applied in a picture-frame-like pattern, either by means of screen-printing or dispensing (step 3). Sealant is required in order to make a liquid crystal cell from the two substrates. In addition to sealing the liquid crystal, sealant protects the liquid crystal from contamination from external sources such as the penetration of water, and from environmental changes. Next, spacers are sprayed to keep a uniform cell gap between the lower and upper substrates (step 4). It is an important requirement to perform the spraying uniformly over the entire substrate, thereby controlling the spacer density (number of spacers per unit area), and preventing the formation of lumps. The spraying technique includes a wet method of spraying spacers and a dry method of spraying spacers. The wet method of spraying spacers involves the following steps: diffusing spacers in a low-boilingpoint organic solvents, such as freon or alcohol, through the use of ultrasonic waves; spraying the spacer-diffused liquid; and drying the panel in order to evaporate the solvent. In the dry method, spacers are applied electrostatically, or diffused by means of an air-jet. When TFT-LCDs are handled, measures should be taken to prevent a buildup of static electricity. In addition, fren, alcohol, and other organic solvents are subject to density control. Because of this, the dry or air-jet diffusion method is mainly used. Sequentially, two substrates are assembled with and attached to each other (step 5). Alignment of the two substrates depends on an alignment error, which are several micrometers. When the two substrates are aligned with each other beyond the alignment error, since light leakage may occur, desirable display characteristics cannot be obtained. The next step is a cell-cutting process (step 6). The liquid crystal cell manufactured through the foregoing five steps is cut into unit cells. The liquid crystal cell undergoes the cell-cutting process after a plurality of liquid crystal cells is formed on the large-sized glass substrate. The cell-cutting process includes a scribing process that forms a cutting line on a surface of the substrate with a pen of a diamond having a higher hardness than the glass substrate, and a breaking process that breaks the liquid crystal cell into unit cells. Then, a liquid crystal is injected into the cell gap between the two substrates (step 7). The unit liquid crystal cell generally has an area of hundreds of CLIENT INPUT NEEDED and a gap of several micrometers (CLIENT INPUT NEEDED). A vacuum injecting method, which uses a pressure difference between inside and outside of the cell fills the liquid crystal between the two substrates.
As shown in FIG. 2A, a cut potion xe2x80x9cAxe2x80x9d of the unit liquid crystal cell is so sharp that workers may receive injuries in subsequent processing. Therefore, the cut portion xe2x80x9cAxe2x80x9d should be ground. In other words, as shown in FIG. 2B, the cut portion xe2x80x9cAxe2x80x9d needs to be ground in order to make upper and lower surfaces 10 and 12 have a predetermined inclined angle.
FIGS. 3A and 3B show a conventional method of grinding the liquid crystal cell. As shown in FIG. 3A, a conventional apparatus of grinding the liquid crystal cell includes a rotation axis 50 and a grinding wheel 52 mounted to the rotation axis 50. Also, FIG. 3B shows a grinding method of the lower edges of the liquid crystal cell. In the convention method of grinding the cut portion of the liquid crystal cell, upper and lower edges of the cut portion xe2x80x9cAxe2x80x9d are separately ground. However, since such a grinding method grinds the upper and lower edges of the cut potion of the liquid crystal cell, respectively, it has a disadvantage in that the processing time is long.
For the foregoing reason, there is a need for an apparatus for grinding the liquid crystal cell and having a short processing time.
To overcome the problems described above, preferred embodiments of the present invention provide an apparatus and a method of grinding a liquid crystal cell during a short processing time.
In order to achieve the above object, a preferred embodiment of the present invention provides an apparatus for grinding a liquid crystal cell comprising a power unit; a first axis receiving a rotational motion from the power unit; a second axis extending from the first axis and rotating along with the first axis; a first grinding wheel having a first grinding surface and being arranged between the first and second axes, the first grinding surface having a first inclined angle; and a second grinding wheel having second and third grinding surfaces and being arranged at a terminal portion of the second axis, the second grinding surface having a second inclined angle, and the third grinding surface having a third inclined angle.
The first and second grinding wheels have a substantially circular shape. A distance between the first and second grinding wheels is controllable. Rotation speeds of the first and second axes are substantially equal. The first and second inclined angles are about 30 degrees. The third inclined angle is between approximately 80 degrees and 90 degrees.
The preferred embodiment of the present invention, in another aspect, further provides a method of grinding a liquid crystal cell including: providing a grinding apparatus on at least one corner of the liquid crystal cell, the grinding apparatus including a first wheel and a second wheel; grinding the corner of the liquid crystal cell; inserting the liquid crystal cell between the first wheel and the second wheel, the liquid crystal cell having at least one cut portion; and grinding the cut portion of the liquid crystal cell.
The step of grinding the cut portion includes grinding the upper and lower edges of the cut portion simultaneously.
By using the grinding apparatus according to the preferred embodiment of the present invention, since the upper and lower edges of the cut portion of the liquid crystal cell are ground simultaneously, the processing time can be reduced remarkably.